The present invention relates to apparatus for draining of moisture from the air pressure system of vehicles and, more specifically, to apparatus for automatically draining the moisture upon shut down of the vehicle.
A common form of braking system upon large trucks is that truck which operates upon air pressure. The truck engine operates an air compressor which provides the pressure for the braking system. The air pressure is stored generally in a pressure storage tank appropriately located within the vehicle in order that a constant pressure supply may be available.
During operation of the air compressor, air is pulled from the atmosphere and compressed by the air compressor. Atmospheric air contains moisture which, upon compression, causes the moisture to condense. Throughout continued use of the pressure system, the moisture will build up in the form of liquid in the pressure storage tank.
Continued presence of moisture in the air brake system can cause considerable harm to the system and even brake failure. For example, the moisture can cause deterioration of rubber seals and the like. Additionally, in cold weather, where the moisture has migrated into the pressure lines and other aspects of the braking system, it can freeze causing malfunction or total failure of the braking system.
For the foregoing reasons, it is essential that the moisture, which eventually accumulates in the pressure storage tank, be drained from the tank before it builds to a level to migrate into the remainder of the braking system. A conventional means for removing moisture from the braking system and, more particularly, from the pressure storage tank is to utilize a separate tank positioned below the pressure storage tank and interconnected with the pressure storage tank by means of a check valve. This separate tank, known as a wet tank, will draw the collecting liquid or moisture from the pressure storage tank by means of gravity into the wet tank.
During normal operation, the wet tank, which has a drain valve in the bottom thereof, operates with the drain valve closed and the moisture accumulating in the pressure storage tank will drain by gravity into the wet tank. Periodically and usually at the end of every day when the vehicle is shut down, the drain valve on the wet tank is manually opened. The check valve between the pressure storage tank and wet tank will then go into a closed position and the moisture which has accumulated in the wet tank, by means of the pressure already present therein, will blow the moisture out of the wet tank and purge the system.
The foregoing system for draining of moisture from the air braking system of a vehicle, if operated properly, will be effective. However, one of the severe drawbacks of such a system is that the operators of the vehicle forget to drain the wet tank. After a period of time, the wet tank will fill and the moisture will back up into the pressure storage tank and ultimately into the system with grave consequences.
What is needed in the industry is a means by which the wet tank can automatically be drained whenever the vehicle is in a shut down mode. Equally important however is that such an automatic draining system be of the type and nature that a failure of the system to drain during shut down of the vehicle will work in a fail-safe mode, i.e. upon a failure of the drain system to work automatically pressure will not be released from the pressure system which would, of course, render the braking system inoperative and thus create a dangerous situation.